Avoid code duplication inside String::append()

The implementation of 'append(UChar)' had been repeated inside 'append(LChar)', this duplication is obviated now.

Review URL: https://chromiumcodereview.appspot.com/18201004

git-svn-id: svn://svn.chromium.org/blink/trunk@153486 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move line endings detection and offset-based TextPosition construction into TextPosition.h

This refactoring is necessary to allow reporting of (line, column) for CSS errors.

R=pfeldman, vsevik, jochen
BUG=none

Review URL: https://chromiumcodereview.appspot.com/18542002

git-svn-id: svn://svn.chromium.org/blink/trunk@153487 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Disable sourceUrl and SourceMappingUrl deprecation warnings for a few releases.

BUG=256636

Review URL: https://chromiumcodereview.appspot.com/18580011

git-svn-id: svn://svn.chromium.org/blink/trunk@153488 bbb929c8-8fbe-4397-9dbb-9b2b20218538